1. Field of the Invention
This invention relates generally to an apparatus and method for protecting a semiconductor device, and more particularly to an apparatus and method for protecting a microprocessor from damage due to shock and/or vibration, thermal overheating due to high heat flux between the microprocessor die and thermal plate and lack of thermal interface material.
2. Description of the Related Art
A number of different approaches have been tried to protect microprocessors from damage due to shock and/or vibration and thermal problems created by overheating. In one approach, the processor die is placed in direct contact with the pedestal portion of a thermal plate. This approach is an acceptable design from a thermal perspective for low heat fluxes because it permits heat to transfer directly from the processor die to the thermal plate. However, it may not be structurally sound because exterior shocks or vibrations imparted to the thermal plate are transmitted directly to the die.
In a modified version of this approach, a protective plastic or alternate material "donut" spacer is placed between the OLGA (Organic Land Grid Array) and the thermal plate. The protective donut is provided to absorb any shock and/or vibrations that may be imparted from the thermal plate to the die. The protective donut is not designed, however, to conduct heat. In an alternate approach, a grease layer is placed between the processor die and the pedestal. The thickness of the grease layer may vary between 0.002 inches and 0.009 inches. The maximum thickness is determined from the total tolerance across the interface between the OLGA and the thermal plate. In this approach, plastic donut spacers may also be provided between the OLGA and thermal plate to absorb shocks and/or vibrations imparted to the thermal plate.
With these approaches, the thickness of the pedestal extending from the thermal plate to the processor die must be tightly controlled. If it is not, shock or vibration applied to the thermal plate can cause the processor to become damaged, even in the designs utilizing the donut spacers. Maintaining a tightly controlled pedestal thickness is a difficult and expensive processing step in the overall construction of the microprocessor. Furthermore, with this design the thermal interface is somewhat thick. It has been found that the thicker the thermal interface is, the greater the thermal resistance from the processor die to the thermal plate will be, which in turn negatively impacts how quickly the processor die is cooled.
Furthermore, these approaches have limited applicability in that they are only capable of protecting microprocessors that operate at lower heat fluxes and associated lower performance. Future processors operating at higher frequencies will exceed the power limitations of these designs.